From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: problem wit svm_get_msr on kvm-kmod-2.6.31.6 Date: Mon, 16 Nov 2009 13:03:45 +0100 Message-ID: <4B013FA1.4050003@siemens.com> References: <90D306BE6EBC8D428A824FBBA7A3113D014275E0F0@ronja.maurer-it.com> <4B012709.20508@redhat.com> <90D306BE6EBC8D428A824FBBA7A3113D014275E0F2@ronja.maurer-it.com> <4B012EDF.7030109@redhat.com> <90D306BE6EBC8D428A824FBBA7A3113D014275E0F5@ronja.maurer-it.com> <4B013F2A.2040900@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Dietmar Maurer , kvm To: Avi Kivity Return-path: Received: from david.siemens.de ([192.35.17.14]:20752 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752624AbZKPMD4 (ORCPT ); Mon, 16 Nov 2009 07:03:56 -0500 In-Reply-To: <4B013F2A.2040900@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > On 11/16/2009 01:17 PM, Dietmar Maurer wrote: >> 38f0: 0f 85 82 01 00 00 jne 3a78 >> 38f6: 48 8b 87 e0 27 00 00 mov 0x27e0(%rdi),%rax >> 38fd: 48 8b 48 50 mov 0x50(%rax),%rcx >> 3901: 0f 31 rdtsc >> 3903: 48 01 c8 add %rcx,%rax >> >> # this is svm_get_msr+0x146 >> 3906: 48 89 02 mov %rax,(%rdx) >> > > > Looks like a miscompile of native_read_tsc(), it needs to use %edx:%eax, > not assume the result is in %rax. > > Jan, looks like the culprit is > > static inline unsigned long long kvm_native_read_tsc(void) > { > unsigned long long val; > asm volatile("rdtsc" : "=A" (val)); > return val; > } > > "=A" only works correctly on i386, need to use "=a" "=d" for portability. > Yes, already commit a fix, currently propagating it through all series. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux